Last summer WIRED revealed that Nasa's Eagleworks Lab was testing a copy of the EmDrive, a propulsion device frequently labelled as "impossible" because it appears to violate the law of conservation of momentum. Against all expectation they found it produced thrust. The response from the scientific community was dramatic, and generally sceptical -- but the "anomalous thrust" stubbornly refuses to disappear as more research zeroes in on it.
The situation is not helped by garbled media reports like "British scientist who says he's found the secret of Star Trek's 'warp speed'". But the subject is attracting serious examination from scientists who want to know if a sealed cavity filled with resonating microwaves can really produce net thrust. Previously the effect has been measured by British scientist Roger Shawyer, who invented the EmDrive, and a Chinese team, as well as Nasa.
Martin Tajmar, professor and chair for Space Systems at the Dresden University of Technology, is perhaps uniquely well qualified to evaluate the EmDrive. His research interests include "Breakthrough Propulsion Physics," space drives which do not rely on the variations on rocket thrust but which draw on more exotic science.
